JP2001233528A - Sheet feeder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely separate curvedly, at a separating position S, a paper P sucked electrostatically to a transfer belt 46. SOLUTION: A recessed groove 411 through the entire peripheral surface is formed generally at the lateral center position of a drive roller 41 disposed at a position corresponding to a separation position S, and a transfer belt 46 is recessed by the recessed groove 411. Because a sheet P passing through the separation position S produces a deflection generally at the lateral center portion thereof, the sheet P can provide a strong stiffness in the feeding direction thereof. Thus, even a sheet with weak stiffness such as thin sheet can be surely separated curvedly at the separation position S.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a facsimile machine, a scanner, a printer, and the like.
The present invention relates to a paper transport device that transports paper such as a document and transfer paper.

[0002]

2. Description of the Related Art In a paper conveying apparatus used in a copying machine or the like, an endless conveying belt wound around a plurality of rollers is used as a means for applying a conveying force to a sheet on a sheet conveying path. There is. Such a transport belt is generally configured such that a position corresponding to the roller on the most downstream side around which the transport belt is wound is a separation position, and the transport belt is separated from the paper transport path along the curvature of the downstream roller. Thus, the paper is separated from the conveyor belt by curvature.

[0003]

However, with such a conveyor belt, the paper having a weak so-called stiffness, such as a thin paper, cannot sufficiently obtain the curvature separating function, and adheres to the conveyor belt from the separation position. In some cases, the paper jams and gets caught in the transport path, causing a jam or the like.

[0004] In particular, when a sheet or a conveyance belt is charged, the sheet is electrostatically attracted to the conveyance belt and is hardly separated. For example, when a transfer roller or the like is provided inside the transport belt and a transfer bias or the like is applied to the sheet via the transport belt, the sheet and the transport belt carry a charge for the transfer bias and the charge elimination thereof. Therefore, the paper is electrostatically attracted to the transport belt, and the above-described problem is likely to occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a paper transport apparatus which has a simple structure and can reliably separate paper from a transport belt at a predetermined separation position. Aim.

[0006]

According to the present invention, there is provided a paper transporting apparatus including a transport belt which is formed in an endless shape and transports paper by performing a circulating operation. A concavity is formed inside the passage area of the sheet at the separation position where the conveyance belt is separated, inward of the conveyance belt.

[0007] According to such a configuration, since the concave portion inward of the transport belt is formed at the separation position where the paper is separated from the transport belt, the paper passing through the separation position is provided with the transport belt. A small deflection is formed corresponding to the dent, thereby giving a strong stiffness in the transport direction. Therefore, the sheet can be surely separated from the conveyance belt by the curvature at the separation position.

It is desirable that the depth of such a dent of the transport belt is 0.4 mm or more. In this way, as will be apparent from the experimental results described later, it is possible to surely obtain high paper separation.

Preferably, the recess of the transport belt is formed at a position corresponding to a substantially central portion in the width direction of the sheet passing through the separation position.

[0010] According to this configuration, since the minute deflection of the sheet passing through the separation position due to the dent becomes substantially symmetric with respect to the width direction of the sheet, the sheet and the conveyance path are located downstream of the separation position in the conveyance direction. Even if contact occurs, an appropriate transport state can be obtained without causing oblique transport or the like.

[0011] Further, as a specific configuration for forming a recess in the conveyor belt, the conveyor belt has a circular cross section of the same diameter over the entire width, and the conveyor belt is wound around a position corresponding to the separation position. It is preferable that a roller be provided, and the roller be formed with a concave groove over the entire circumference inside the paper passage area at the separation position.

With this arrangement, at the separation position, a dent can be formed in the transport belt wound around the roller having the groove, so that the sheet passing through the separation position has a small deflection. By forming the sheet, a strong stiffness is given in the conveyance direction, and the sheet can be surely separated from the conveyance belt by the curvature at the separation position.

Further, such a roller has a circular cross section of the same diameter over the entire width and forms a concave groove only at a predetermined position inside a region corresponding to the sheet at the separation position. It can be easily manufactured only by cutting a concave groove at a predetermined position on a round bar material.

Further, the concave groove of the roller has a depth of
Desirably, it is 0.5 mm or more. By doing so, as is clear from the experimental results described later, it is possible to surely cause the paper passing through the separation position to bend so as to promote the curvature separation, and thereby to promote the curvature separation. Is sufficiently obtained.

If the width of the groove of the roller is too narrow, the groove is absorbed by the conveyor belt, while
If it is too wide, the width of the paper in the paper width direction will be too wide,
The paper cannot be sufficiently stiffened, and the paper passing through the separation position may become unnecessarily bent, causing wrinkles and the like downstream of the separation position in the transport direction. For this reason, as apparent from the experimental results described later, the width of the concave groove of the roller is 3
It is desirable that it is not less than 15 mm and not less than mm. Furthermore, it is preferable that it is 5 mm or more and 15 mm or less.

As described above, the configuration for prompting the sheet separation is as follows.
It is particularly preferably applied when transfer bias applying means for applying a transfer bias to a sheet conveyed by the conveyance belt is provided inside the conveyance belt via the conveyance belt. it can.

That is, in a transport belt (so-called transfer belt) in which a transfer bias applying means is disposed inside, the transport belt and the paper on the transport belt are charged by a transfer bias or the like, and both of them are electrostatically attracted to each other. Although separation is easily hindered, if a dent is formed in such a conveyance belt, a strong stiffness in the conveyance direction can be given to a sheet passing through the separation position. At the separation position, the sheet can be surely separated from the conveyance belt by a curvature.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration of an image forming apparatus to which a sheet conveying device according to the present invention is applied. As shown in this figure, the paper P placed on the paper feed tray 10 is
Is a paper feed roller 11 which is normally rotated by the advance roller 13
The sheet is fed into the nip portion between the sheet feeding rollers 12 rotating in the reverse direction, and the sheet at the uppermost position is separated to form a pair of registration rollers 14.
Will be fed up. The registration roller pair 14 aligns the leading edge of the sheet P, and feeds the sheet P toward the transfer position T at a timing when a toner image formed on the photoconductor 30 described later reaches the transfer position T.

Around the photoreceptor 30, a charger 31 for charging the surface of the photoreceptor 30 to a predetermined potential in the direction of rotation thereof is selectively exposed to the surface of the photoreceptor 30 to lower the potential. And an exposure device 32 for forming an electrostatic latent image, a developing device 33 for developing the electrostatic latent image with toner to form a toner image on the photoconductor 30, and applying the toner image on the photoconductor 30 to paper P A transfer unit 40 for transferring and a cleaner 34 for removing toner remaining on the surface of the photoconductor 30 are arranged. In this apparatus, reversal development is performed using positively charged toner.

The transfer unit 40 includes a drive roller 41, a driven roller 42, a transfer roller 43, support rollers 44 and 45, and an endless transfer belt 46 wound around these rollers. A potential of a polarity (minus) opposite to that of the toner image on the photoconductor 30 is applied to the transfer roller 43, and a charge is applied to the sheet P located at a transfer position T on the transfer belt 46 via the transfer belt 46. Transfer is performed. Further, the transfer belt 46 is driven to circulate by the drive roller 41, and conveys the sheet on the transfer belt 46 further downstream of the conveyance path. The configuration of the transfer device 40 will be described later in detail.

The paper P on which the toner image has been transferred at the transfer position T is further fed between the heating roller 15 and the pressure roller 16 to fix the toner image thereon.
7, the sheet is discharged onto a discharge tray 18. In FIG. 1, reference numeral 20 denotes a transport path of the sheet P.

Next, the transfer unit 40 in this embodiment will be described with reference to FIGS.

As described above, the transfer belt 46 is wound around the drive roller 41, the driven roller 42, the transfer roller 43, and the support rollers 44, 45.
Circulates due to the rotation of the roller, and functions as a transport belt that transports the paper. The transfer belt 46 is configured as an endless belt formed of urethane rubber having a thickness of 0.6 mm, and has a fixed width equal to or larger than the full width of the maximum size paper (for example, A3 size paper) conveyed by the apparatus. I have.

The transfer roller 43 is composed of a sponge roller made of conductive synthetic resin, and has a transfer position T.
Is elastically in contact with the transfer belt 46 below. Then, a negative potential having a polarity opposite to that of the toner is applied as a transfer bias by a constant current control of about −45 to 50 μA from a power source (not shown) to charge the sheet P located at the transfer position T.

The driven roller 42 is disposed below the transfer position T on the upstream side in the sheet transport direction, and applies a predetermined tension to the wound transfer belt 46 while the driven roller rotates in accordance with the circulation operation of the transfer belt 46. It is supposed to.

The support rollers 44 and 45 are disposed upstream and downstream of the transfer position T, support the transfer belt 46 near the transfer position T, and support the transfer belt 46 and the photosensitive member 30.
The contact state is kept constant.

The driving roller 41 is disposed at the most downstream side of the transfer path of the sheet P by the transfer belt 46, that is, at a position corresponding to the separation position S where the sheet P is separated from the transfer belt 46, as described above. The transfer belt 46 wound around is driven to rotate by a driving means (not shown). The drive roller 41 is made of a conductive metal (for example, aluminum alloy) having a diameter of 17.45 mm, and is made of a transfer belt 4.
6 is configured as a round bar member having a circular cross section of the same diameter over substantially the entire width around which the member 6 is wound.

A groove 411 is formed in the drive roller 41 over the entire circumference of the drive roller 41 at a position corresponding to a substantially central portion in the width direction of the sheet P at the separation position S. This concave groove 411 has a width L = 5 m by cutting.
m, a groove having a substantially arc-shaped cross section with a depth D of the deepest part = 1.5 mm. Due to the concave groove 411, the transfer belt 46 is positioned at a substantially central position in the width direction of the separation position S.
A slight recess of about 1 mm is formed inward.

In such a transfer device 40, the transfer belt 4
When there is no paper at the transfer position T, the toner adhering to the photoreceptor 30 may be picked up, or toner may be scattered to transport the paper to which unfixed toner has adhered, and the toner may adhere. However, when the toner adheres to the transfer belt 46, it causes a back stain on the subsequent sheet P. Therefore, a cleaning device 50 for removing the toner attached to the transfer belt 46 is provided in parallel with the transfer device 40.

The cleaning device 50 includes a power supply 51 for applying a toner removing bias of the same polarity (plus) as the toner to the driving roller 41 and a fur brush 5 grounded.
And the power supply 51 is connected to the drive roller 41 by 2
A toner removal bias of about 0 μA is applied, and 1.5 KV to 2.
By applying a potential difference of about 0 KV, the toner is floated from the transfer belt 46, and the thus floated toner is fur brush 52 made of a large number of polyester resin fibers rotated in the same direction as the transfer belt 46 by a motor (not shown). It is designed to be scraped off.

The toner scraped off from the transfer belt 46 by the fur brush 52 is collected below the fur brush 52 by a casing 53, and is collected in a toner collecting container (not shown) by an auger 54 that is rotated by a motor (not shown). It has become.

In the image forming apparatus (paper transporting apparatus) configured as described above, the paper P transported by the transfer belt 46 has a polarity opposite to that of the toner due to the transfer bias applied from the transfer roller 43 at the transfer position T. Is negatively charged. On the other hand, the transfer belt 46
In the vicinity, the toner is positively charged with the same polarity as the toner by the toner removal bias applied to the drive roller 41. Therefore, in the vicinity of the separation position S, the paper P
The transfer belt 46 and the transfer belt 46 are charged to have polarities opposite to each other, and the paper P is electrostatically attracted to the transfer belt 46, so that the two are hardly separated from each other.

However, in this image forming apparatus (paper transporting apparatus), a groove 41 extending over the entire circumference is provided at a substantially central position in the width direction of the driving roller 41 disposed at a position corresponding to the separation position S.
1 is formed, and the transfer belt 46 is formed by the concave groove 411.
As shown in FIG. 2, the paper P passing through the separation position S is slightly bent downward at a substantially central portion B in the width direction of the sheet P, since a concave portion inwardly is formed on the outer surface of the sheet P. Thus, a state is provided in which a strong stiffness is provided in the transport direction.

Therefore, paper having a small thickness, recycled paper,
Even if the paper originally has a low stiffness such as a paper containing moisture, the strong stiffness in the transport direction can be obtained by the above-described bending, so that the transfer belt 46 can be reliably positioned at the separation position S against the electrostatic attraction force. Can be separated from

Further, since the deflection is formed at a substantially central portion B in the width direction of the sheet P, even if the sheet P that has passed through the separation position S comes into contact with the transport path on the downstream side in the transport direction, the sheet P is not obliquely transported. An appropriate transport state can be obtained without any occurrence.

A concave groove 411 for improving the sheet separating performance.
Can be formed by performing cutting or the like on a portion, such as the center, of the entire width of the drive roller 41, so that, for example, compared to a case where a ridge protruding from the outer surface of the drive roller 41 is formed. Then, it can be easily manufactured.

Next, a description will be given of the relationship between the size of the groove 411 and the sheet separating property obtained by an experiment in which the width L and the depth D of the groove 411 are appropriately changed.

[0039]

[Table 1]

Table 1 shows the results when the width L of the concave groove 411 is variously changed. Note that the depth D of the concave groove 411 is 2.0
mm. The drive roller 41 was applied with a toner removal bias of 20 μA as a round bar made of an iron-based material and having a diameter of 17.45 mm. The transfer belt 46 is 0.6 m thick
m of urethane rubber.

According to the experimental results shown in Table 1, the groove 4
If the width L of the sheet 11 is 20 mm or more, sufficient separation of the sheet cannot be obtained, and the transfer belt 46 will be wrinkled, and the sheet P that has passed through the separation position S will be loosened, and will be wrinkled by the fixing process. Was formed.

On the other hand, when the width L of the concave groove 411 is smaller than 3 mm, no dent is formed on the transfer belt 46, and no improvement in the sheet separating property is recognized. When the width L of the concave groove 411 was 3 mm, a 0.4 mm dent was formed in the transfer belt 46, and it was confirmed that the separation property of the paper was improved although it was insufficient. In Table 1, the depth of the depression on the belt surface indicates the average depth of the depression observed in the transfer belt 46 during the circulation operation. The same applies to Table 2 described later.

From this experimental result, the width L of the concave groove 411 is
A range of 3 mm or more and 15 mm or less is a preferable range in which the improvement of the paper separation property is recognized, and a range of 5 mm or more and 15 mm or less is an optimum range in which particularly excellent paper separation property is recognized. Further, it can be said that it is desirable that the concave groove 411 has a width capable of forming a concave in the transfer belt 46.

[0044]

[Table 2]

Table 2 shows the results when the depth D of the concave groove 411 is variously changed. The width L of the concave groove 411 is 5 m
m and kept constant. Drive roller 41 and transfer belt 46
Are the same as those in Table 1 above.

According to the experimental results shown in Table 2, the groove 4
It was found that when the depth D of No. 11 was 0.3 mm or less, no effect on the paper separation property was obtained. This is the transfer belt 4
6 is 0.6 mm, it is considered that the concave groove 411 that is excessively shallower than this thickness is absorbed by the elastic deformation of the transfer belt 46. However, in the case of 0.5 mm, which is shallower than the thickness of the transfer belt 46,
Almost sufficient improvement in paper separation was observed. The dent formed on the belt surface at this time was 0.4 mm in depth.

On the other hand, the depth D of the concave groove 411 is 0.5 mm
With the above, sufficient paper separability was obtained, and it was found that there was no upper limit from the viewpoint of paper separability. This is groove 4
If the depth 11 is deeper, the inwardly recessed portion of the transfer belt 46 does not contact the bottom of the groove 411, and the depth D of the groove does not substantially affect the state of the transfer belt 46. .

From the results of this experiment, the depth D of the concave groove 411 was
Can be said to be a suitable range in which an improvement of the paper separation property is sufficiently recognized to be 0.5 mm or more. In addition, concave groove 4
It can be said that 11 preferably has a depth capable of forming a recess in the transfer belt 46. Further, it can be said that the recess of the transfer belt 46 is more preferably 0.4 mm or more in depth.

Although the present invention has been described with reference to the embodiment, the paper transporting apparatus according to the present invention is not limited to the above embodiment, and may be configured as follows.

(1) In the above embodiment, a transfer belt provided with a transfer roller is used as a transfer belt for promoting curvature separation. However, the present invention relates to a transfer belt for transferring sheets by circulating. If so, the present invention may be applied to other transport belts such as a feed belt of a feed unit.

(2) In the above embodiment, the roller provided at the position corresponding to the separation position S and provided with the groove is the drive roller 41 for driving the transport belt (transfer belt 46). It is not necessary to use a drive roller for driving the transport belt.

(3) In the above embodiment, the grooves 411 are used to remove toner from the transport belt (transfer belt 46).
Is configured to apply a positive potential to the roller (drive roller 41) provided with the roller, but the present invention is not limited to a configuration in which such a potential is applied to the roller.

(4) In the above embodiment, the paper conveying apparatus according to the present invention is applied to an image forming apparatus such as a copying machine, a facsimile apparatus and a printer. However, an image reading apparatus such as a copying machine, a facsimile apparatus and a scanner apparatus is used. May be applied.

(5) In the above embodiment, a roller having a concave groove 411 (a driving roller 4
Although 1) is formed, for example, a roller having a groove between the two round bars may be configured by arranging two round bars coaxially in parallel with a predetermined gap therebetween. Good.

(6) In the above embodiment, the roller (drive roller 4) around which the transport belt (transfer belt 46) is wound
Although the recess is formed in the transport belt by forming the concave groove 411 in 1), if the recess can be formed in the transport belt,
It is not limited to the above embodiment. For example, a configuration may be employed in which a recess is formed on the front side of the transport belt by changing the thickness of the transport belt itself in the width direction orthogonal to the paper transport direction. However, in the transfer belt in which the transfer roller is disposed inside as in the above-described embodiment, the transfer belt has a uniform thickness in order to apply a uniform transfer bias in the width direction to the sheet. It is desirable to form a recess in the transfer belt by a configuration such as a roller that is wound around.

[0056]

As described above, according to the paper conveying apparatus of the present invention, since the concave portion inward of the conveying belt is formed at the separation position where the paper is separated from the conveying belt, The paper passing through the position is formed with a small deflection corresponding to the dent of the transport belt, thereby giving a strong stiffness in the transport direction. Therefore, the sheet can be surely separated from the conveyance belt by the curvature at the separation position.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of an image forming apparatus to which a paper transport device according to the present invention is applied.

FIG. 2 is a schematic perspective view of a transfer device.

FIG. 3 is a plan view of a portion near a driving roller.

[Explanation of symbols]

 40 transfer unit 41 drive roller 411 concave groove 43 transfer roller 46 transfer belt P paper T transfer position S separation position

Claims (7)

[Claims] A transport belt that is formed in an endless shape and transports the paper by performing a circulating operation, wherein the transport belt is provided inside a paper passage area at a separation position where the paper is separated from the transport belt. A sheet conveying device, wherein a concave portion is formed in an inner side of the conveying belt. 2. The transfer belt according to claim 1, wherein the recess has a depth of 0.4.
The sheet conveying device according to claim 1, wherein the distance is equal to or more than mm. 3. The sheet conveying device according to claim 1, wherein the recess of the conveying belt is formed at a position corresponding to a substantially central portion in the width direction of the sheet passing through the separation position. 4. It has a circular cross section of the same diameter over the entire width,
A roller provided with the transport belt wound around the position corresponding to the separation position, wherein the roller has a concave groove formed all around the paper passage area at the separation position. The sheet transporting device according to claim 1, wherein: 5. The concave groove of the roller has a depth of 0.
The sheet conveying device according to claim 4, wherein the length is 5 mm or more. 6. The concave groove of the roller has a width of 3 mm.
At least 15 mm or less.
6. The paper transport device according to any one of 5. 7. A transfer bias applying means for applying a transfer bias to a sheet conveyed by the conveyor belt via the conveyor belt is provided inside the conveyor belt. Item 7. A sheet transport device according to any one of Items 1 to 6.